A friend of my just took her machine with this problem. Didn't have embroidery foot on, just the sewing foot. She felt DUH! This is why i just embroidery with mine.

Is the thread nest under the stitch plate or under the hoop?
What type of fabric and stabilizer are you using when this happens?
what type of design does this happen to?

When you thread your machine is your pressure foot up and after thread breaks are you threading the machine with the pressure foot up?

Are you making sure the top thread is in the top thread tension disk and is the bobbin thread clicking into the bobbin tension on the bobbin case when your threading the machine?

Have you cleaned the bobbin area out to get any lint or thread pieces out?
Did you try a new needle?

More information would help us help you!! LOL
EastWitch2

Another thing you may want to check- has the thread jumped out of the take-up lever(thing that goes up and down before thread goes to needle). Just wanted to clarify it because people call it many different things.

I've had this problem when using too light of stabilizer. So am learning to do two things 1)Use a quality stabilizer& if not hooped add some spray fabric adhesive. 2)Change the needle after 35-40 or so hours(I prefer the titanium needles for embroidery too). Hope this helps you some.:~D

When this happens to me it's usually because I've put the bobbin back in up-side-down. xXx